Just because "Sesame Street" is entering its 33rd season today doesn't mean Aloysius "Snuffy" Snuffleupagus needs a makeover. After all, he's supposed to be only 4 years old anyway. But the times change, even at 123 Sesame St., and the most-watched kids' show on the planet is going modern -- again.

"We're calling it the 33rd experimental season of 'Sesame Street,' " laughed co-executive producer Arlene Sherman, who's been on board for 25 of those years.

"Sesame Street" (8:30 a.m. Mondays-Fridays, Channel 9) has always considered itself a work in progress and constantly checks its progress along the way, both in an academic fashion (how children learn has changed through the years) and with an eye toward entertainment.

The last "big change" was in season 30, when Elmo got his own segment. That worked phenomenally well -- as anyone who fought for a Tickle Me Elmo doll a couple of Christmases ago can attest. Now Elmo has become, along with "the icon of 'Sesame Street,' " Big Bird, one of the two most popular characters.

But the change that unfolds on the Street today is probably the biggest ever, Sherman said, since the material in each episode (normally a hodgepodge of bits, some of them evergreen) will be 90 percent new this season.

The biggest reason for the change was, pardon the adult industry jargon, a shift in demographics. Yep, younger kids are watching. The target audience is now 2- to 4-year-olds, with even younger ones watching as well. "That changes the way you present the show," Sherman said.

The "classic" players on "Sesame Street" will still be there, but there will be a different look and tone from here on out.

"We basically deconstructed the show," Sherman said. "It's not a magazine format anymore. It's more like the 'Sesame' hour. Children will be able to navigate through it easier."

Each episode's "Street story" won't be interrupted by the now-familiar video or animated breaks of the past. Instead, there will be more narrative and more set structure (kind of like the way "Elmo's World" takes up the last 15 minutes of each episode). Look for expanded roles for Cookie Monster (he'll introduce the letter of the day each episode) as well as Count von Count (who will introduce the number of the day), a new "Spanish word of the day" segment and a significant boost for Ernie, whose new segment, "Journey to Ernie," sends Big Bird on a hunt for Ernie, using modern technology along the way.

"Monster Clubhouse" will be more prevalent. Classic clips of "Bert and Ernie" will be seen in the "Journey to Ernie" skits. Rosita, Zoe and a new character, Lulu, will pal around more together. And Grover will deliver the mail on the street, among numerous other changes.

Sherman called the look "startlingly different." She said the producers and writers, working in conjunction with the show's educators and advisers, worked up a test episode, showed it to kids for their response and comprehension, then "went without fear and judgment and did it."

She laughed, of course. You don't tinker with a classic without some intense worrying. But "Sesame Street" periodically looks at itself and where the rest of the world is, then adjusts (hence the first episode, which indirectly looks at the events of Sept. 11). Not only were younger children tuning in, but they also were more sophisticated, having grown up with computers and DVD players. Plus, there's incredible competition in the children's television genre, much of it excellent.

"When we started, we were the only game in town," Sherman said. "Now there's whole networks dedicated to children. We have to stay relevant and to motivate the children." She promised that the heart and soul of the work wouldn't change, because that's what drew her to the series all those years ago.

"This show revolutionized television in a lot of ways. I remember saying, 'Wow, this is the hippest thing I've ever seen in my life. This is cool television.' "

The chance to keep "Sesame Street" cool, relevant, smart and funny was a task that, Sherman says, "energized us. It challenged us." One of the main elements was to keep that old "Sesame Street" magic formula intact. "It works on two levels, and we wanted not to dumb it down, and keep it sophisticated."

"We've taken more chances this season than we have cumulatively," Sherman added. But none of that was undertaken without a lot of thought and a little trepidation.